Power consumption is one of the key factors in mobile/wireless communications. A wireless user equipment consumes energy also in idle mode comprising tasks of cell selection and reselection.
In WCDMA technology three codes are provided for cell search and synchronization: primary synchronization code PSC, secondary synchronization code SSC and scrambling code SCRC. The cell search procedure searches new cells and synchronization finds the timing of the cell. The cell search procedure searches new correlation peaks for PSC, the highest group correlation for SSC and finally finds the SCRC of the cell. The PSC provides slot timing and SSC provides frame timing. If the cell is not already in the neighbor list it is a new cell.
In this method the user equipment is searching new cells even when no new cells cannot be found and thus uses the RF part when it is not needed. The RF part is usually the biggest energy consumer in the user equipment; therefore, its use should be minimized.
3GPP, 3rd Generation Partnership Project, develops specifications for third generation mobile phone systems, and also from Release 8 (Rel-8) the next generation specifications often referred to as LTE, Long Term Evolution. The document 3GPP 25.304 v8.8.0, section 5.2.6, discloses Cell Reselection Evaluation Process and methods for limiting cell search procedure. Current WCDMA technology performs the cell search every 5.12 seconds in idle mode. In WCDMA the S-rules are limiting the cell search procedure, where the network delivers S-rules to the user equipment. The network may also signal a limit value for the user equipment.
EP812119 discloses a method in which after making RSSI and possibly also Bit Error Rate/Word Error Rate (BER/WER) measurements the mobile station monitors the rate of change of the received signal strength indication RSSI. If the rate of change is small and remains so, the mobile station is assumed to be in a stationary state. When in the stationary state the mobile station inhibits making neighbor channel measurements for digital control channel DCCH reselection.